From 63e8577d771445715bd70bb536637a419fdbde1a Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Fri, 10 Jan 2020 11:42:04 +0100
Subject: [PATCH] Create a basic LinkedListAllocator type

---
 src/allocator.rs             |  1 +
 src/allocator/linked_list.rs | 48 ++++++++++++++++++++++++++++++++++++
 src/lib.rs                   |  1 +
 3 files changed, 50 insertions(+)
 create mode 100644 src/allocator/linked_list.rs

diff --git a/src/allocator.rs b/src/allocator.rs
index e2b6396a..52ebbd68 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -9,6 +9,7 @@ use x86_64::{
 };
 
 pub mod bump;
+pub mod linked_list;
 
 pub const HEAP_START: usize = 0x_4444_4444_0000;
 pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
diff --git a/src/allocator/linked_list.rs b/src/allocator/linked_list.rs
new file mode 100644
index 00000000..6e547e59
--- /dev/null
+++ b/src/allocator/linked_list.rs
@@ -0,0 +1,48 @@
+struct ListNode {
+    size: usize,
+    next: Option<&'static mut ListNode>,
+}
+
+impl ListNode {
+    const fn new(size: usize) -> Self {
+        ListNode {
+            size,
+            next: None,
+        }
+    }
+
+    fn start_addr(&self) -> usize {
+        self as *const Self as usize
+    }
+
+    fn end_addr(&self) -> usize {
+        self.start_addr() + self.size
+    }
+}
+
+pub struct LinkedListAllocator {
+    head: ListNode,
+}
+
+impl LinkedListAllocator {
+    /// Creates an empty LinkedListAllocator.
+    pub const fn new() -> Self {
+        Self {
+            head: ListNode::new(0),
+        }
+    }
+
+    /// Initialize the allocator with the given heap bounds.
+    ///
+    /// This function is unsafe because the caller must guarantee that the given
+    /// heap bounds are valid and that the heap is unused. This method must be
+    /// called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.add_free_region(heap_start, heap_size);
+    }
+
+    /// Adds the given memory region to the front of the list.
+    unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
+        todo!();
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 250e1ba9..79956351 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,7 @@
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
 #![feature(alloc_error_handler)]
+#![feature(const_fn)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]